A new ad from Mississippi Conservatives PAC says McDaniel's support is hypocritical, since he has criticized a federal earmark of $200,000 for the Rock 'N Roll Hall of Fame. The PAC, which is associated with incumbent GOP senator Thad Cochran, is making a $100,000 statewide buy for the 30-second spot. Watch it below:

McDaniel is challenging Cochran, a 76-year-old six-term Republican, by running to Cochran's right on issues like government spending. Cochran has gained a reputation in Congress as an unrepentant earmark spender.

"Sen. Cochran and his lobbyist friends should look in the mirror," says McDaniel spokesman Noel Fritsch. "When given the opportunity to repair bridges damaged by hurricane Katrina, Sen. Cochran instead voted to spend that money on the wasteful Bridge to Nowhere in Alaska. Why did Sen. Cochran put a boondoggle pork project in Alaska ahead of Mississippi?"

The Mississippi primary will be held on June 3. Both Cochran and McDaniel would be heavy favorites against the likely Democratic nominee, former congressman Travis Childers.